While traditional 2G mobile telephony is used mainly for wireless communication of circuit-switched voice calls, the 3G mobile telephony has been developed to support wireless communication of packet-switched multimedia sessions using IP (Internet Protocol). For example, the communication protocols used for GPRS (General Packet Radio Service) and UMTS (Universal Mobile Telecommunications System) support packet-switched multimedia services.
A user subscribing to a 2G or 3G mobile access network is typically obliged to have a physical SIM (Subscriber Identity Module) card or similar installed in his/her communication terminal, in order to obtain connectivity with the network. The SIM is thus tied to a mobile subscription and holds a subscription identity and various associated security parameters which the terminal must use when registering with the network in order to gain access and connectivity. The SIM card can be moved between different terminals.
The information lodged in a SIM thus includes various “secrets shared with the network that are used for authenticated the subscriber and authorizing him/her to access and use services in the network. In particular, the SIM typically contains information for calculating parameters known as RES (mobile station authentication response), CK (ciphering key), and IK (integrity key) which are used to, in the following order, compared with a parameter called XRES (expected mobile station response) calculated by the network during the authentication procedure, encrypt the traffic and integrity protect the traffic.
As an alternative to traditional billing-based subscriptions, the subscription may be based on a pre-paid or “pay-as you-go” scheme where the user must pay in advance to “load” the SIM card, before being allowed to make calls or use other services. During registration with a public communication services network, the network will then identify the subscription and control its access and call/session time in accordance with the prepaid sum. Hence, the pre-paid connectivity still requires a subscription with the network and a SIM card or similar, along with a certain “infrastructure” associated therewith in the network.
A service and service-delivery control architecture called “IP Multimedia Subsystem” (IMS) has been developed by the 3rd Generation Partnership Project (3GPP) as a platform for handling multimedia services and sessions, commonly referred to as the IMS network. Thus, an IMS network can be used to initiate and control multimedia sessions for any IMS-enabled terminal connected to any type of mobile access network. The terminal must then, in addition to registering with a mobile access network, also register with the IMS network in order to gain access to the multimedia services. IMS basically uses the same registration routines as those defined for 3G access networks.
According to commonly used terminology for 3G, a UMTS SIM or “USIM” application is used for accessing a UMTS network, and an IMS SIM or “ISIM” application is used for accessing an IMS network. Further, the Universal Integrated Circuit Card (UICC) is a movable physical card in the terminal for holding various service applications in multimedia terminals such as an ISIM application and a USIM application, thus corresponding to the SIM card.
FIG. 1 illustrates schematically an IMS-enabled mobile terminal 100 in which a UICC 102 is installed. The UICC 102 holds a USIM application 102a for gaining connectivity with a UMTS mobile access network 104 and an ISIM application 102b for gaining connectivity with an IMS multimedia services network 106, as shown by dashed two-way arrows. Various other service applications for specific multimedia services may also be installed on the UICC 102, not shown.
However, communication network services based on a subscription and/or a SIM application are associated with various problems. As explained above, access to communication services in a mobile access network and/or an IMS network today requires the establishment of a subscription and that a SIM card or similar is issued for installation in a terminal, which is somewhat expensive and time-consuming to manage for both users and network operators. The SIM card and its associated parameters and functions are handled by the HLR (Home Location Register) node in the mobile access network and/or the HSS (Home Subscriber Server) node in the IMS network, respectively.
Further, a WLAN (Wireless Local Access Network) hotspot can be accessed by subscribers from any terminal by just entering a personal password for authentication. With this system, it is possible for anyone to “steal” a password and utilise the network services illegitimately. It is also possible for a network to pose as being another different network since there is no authentication of the network at the user side.
Another example relates to so-called M2M (Machine-to-Machine) modules that are often used for communicating data and information to support the operation of various equipments or systems. A surveillance system, e.g. for a power distribution network or a pipe system, may comprise a great number of distributed sensors configured to communicate various data or information from different locations to a central control station or the like over a mobile access network, using M2M modules as communication terminals. The M2M modules may thus be used to remotely collect data on, e.g., flow rates, pressures, temperatures, and equipment status as an alternative to manual, on-site data collection.
In such systems with distributed M2M modules, subscriptions must be established and a SIM card must be installed in each and every module. This can naturally be perceived as a significant burden, particularly if the subscriptions are relatively short-lived. In 3GPP, it is currently a requirement that the network operator can be switched remotely for M2M modules and that it should be possible to deploy M2M modules without SIM cards.
In 3GPP, efforts are made to provide connectivity solutions without using a physical SIM or UICC card, to further enable the switch of operators remotely. Also, it is desirable to avoid the handling of physical SIM/UICC cards in very unclean and polluted environments as open surfaces in the equipment easily becomes contaminated with the result of malfunction. It is thus generally desirable to reduce the efforts and costs associated with SIM-based subscriptions. A solution referred to as “Soft SIM” has been proposed to avoid the use of physical SIM cards, where a SIM application is delivered electronically without being tied to a physical card. Still, a subscription as well as parameters, keys and other secret data associated with the SIM application must be maintained and administrated for the Soft SIM solution, along with the necessary network infrastructure mentioned above.
In general, establishing a subscription and issuing a SIM card or Soft SIM provides limited flexibility and renders significant start-up costs in terms of both hardware and management. This scheme is therefore particularly unsuitable for short-term subscriptions. A further significant drawback is that the SIM-application may contain parts that are secret to the operator and also for the user, such as cryptographic algorithms and keys. This may result in specific requirements on the hardware of the device. Further, the Soft SIM solution for remotely switching the SIM may require an additional “player” related to the terminal manufacturer to take part in the SIM management. This additional player may thus be needed in order to verify the integrity of a secure element required in the terminal to securely store and compute cryptographic parameters.
Another disadvantage of ordinary SIM-subscriptions relates to making local calls when visiting a foreign country. A costly detour must then be made for the call to the home network in the home country due to the subscription, before connecting to a called local terminal in the visited country.